53 lines
1.4 KiB
C
53 lines
1.4 KiB
C
#include "arena.h"
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#include <assert.h>
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#include <stdlib.h>
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#include <string.h>
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static bool is_power_of_two(uintptr_t x) { return (x & (x - 1)) == 0; }
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static uintptr_t align_forward(uintptr_t ptr, size_t alignment) {
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assert(is_power_of_two(alignment));
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uintptr_t modulo = ptr & (alignment - 1); /* = ptr % alignment */
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if (modulo != 0)
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ptr += alignment - modulo;
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return ptr;
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}
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void arena_init(Arena *arena, void *buffer, size_t buffer_length) {
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arena->buffer = buffer;
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arena->buffer_length = buffer_length;
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arena->offset = 0;
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}
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#ifndef DEFAULT_ALIGNMENT
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#define DEFAULT_ALIGNMENT (2 * sizeof(void *))
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#endif
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void *arena_alloc(Arena *arena, size_t size) {
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return arena_alloc_align(arena, size, DEFAULT_ALIGNMENT);
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}
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void *arena_alloc_align(Arena *arena, size_t size, size_t alignment) {
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/* Align the current offset to the specified alignment */
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uintptr_t curr_ptr = (uintptr_t)arena->buffer + arena->offset;
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uintptr_t offset = align_forward(curr_ptr, alignment);
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offset -= (uintptr_t)arena->buffer;
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/* Check to see if there is some memory left */
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if (offset <= arena->buffer_length - size) {
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void *ptr = &arena->buffer[offset];
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arena->offset = offset + size;
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/* Zero out newly allocated memory */
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memset(ptr, 0, size);
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assert(ptr != 0);
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return ptr;
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}
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abort();
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}
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void arena_clear(Arena *arena) { arena->offset = 0; }
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